Wood chip cleaning process



Dec; 2, 1941. WARD 2,264,421

WOOD CHIP CLEANING PROCESS Filed Aug. 12, 1939 PRIOR HRT NEW PROCESS I INVENTOR Mugs/ 7 ZUZe/wl/ Patented Dec. 2, 1941 2,264,421 WOOD CHIP CLEANING PROCESS Arthur T. Ward, New York, N. Y.

Application August 12, 1939, Serial No. 289,735 4 Claims. (01. 83-45) My present invention relates in general to improvement in the art of manufacturing paper, and relates more specifically to an improved method of preparing wood chips for introduction into the digesters of paper mills.

Generally defined, an object of my invention is to provide an improved process of treating logs and wood chips preparatory to final separation of the fibres thereof in digesting apparatus.

It has long been customary in the art of con-' verting logs into wood fibrein the paper making industry, to follow a well defined mode of procedure. In accordance with this prior typical method, the debarked logs are removed from a stock pile and are initially washed in rotary drums or hot water ponds, or both, after which the individual logs are manually freed of rotted portions and knots by drilling, sawing, splitting and cutting before being delivered to the chippers and chip breakers. The chips are then subjected to a screening action in order to remove sawdust and other granular material, and the oversize chips which are separated by the screens are returned to the chip breaker while the supposedly good chips are sent to the digesters. While certain automatic machines are utilized in carrying on this prior method, agreat deal of expensive and tedious manual labor is required in the removal of the rotten Wood, bark and knots prior to chipping, and this manual operation besides being costly, also results in waste of considerable good fibre bearing material and does not avoid having a great deal of the objectionable substances entering the digesters with the good chips. This prior method therefore frequently results in the production of inferior paper in spite of the exercise of extreme care in an effort to remove the undesirable rotten wood, bark, knots and the like.

It is therefore amore specific object of my present invention to provide an improved process of preparing wood for the digesters in the paper industry, whereby the labor and cost of preparation are reduced to a minimum, and by virtue of which a superior product results.

In order to portray a clear conception of my present improvement as compared to the prior art method, reference may be had to the accompanying drawing forming a part of this specification and.wher ein like reference characters designate the same or similar parts in the two diagrams.

Fig. 1 is a diagram representing the flow sheet of a typical prior art method of treating logs for the production of wood chips; and

Fig. 2 is a similar diagram showing the fiow sheet or steps of my improved process of treattherein, comprised the following specific steps. The debarked logs 3are first pulled or otherwise transferred from the stock pile 4 in the yard, and are deposited in a revolving washing drum 5 from whence they are subsequently deposited in a hot water pond 6. After the logs 3 have been thus thoroughly Washed, they are taken from the pond 6 to a zone 1 where they are manually prepared for subsequent chipping. This preparation in the zone 1 is very tedious as each individual log 3 must be scraped, sawed, bored, split and otherwise treated for the removal of residual bark, rotted or decayed portions and knots. In some mills over a dozen able bodied men are required to do this work, and the cost of thus treating the logs preparatory to chipping averages about one dollar per cord. From the zone '1, the logs 3 are passed through the chipper 8 and from thence the chips may be subjected to breaking before being delivered to the final screen 9. The screen 9 is ordinarily of the multiple deck type and removes the very fine particles such as sawdust from the coarser material,

and deliversthe fines to the boilers or otherwise. The screen '9 also removes the over-size chips and sends these to a chip breaker ID from whence they are returned for further screening, and the supposedly good and finally treated chips are sent to the digester for conversion into pulp. It has been found, that even by exercising the greatest care in the zone I, it is impossible to prevent undesirable material from entering the digesters, since this prior method of removing the bark, decayed wood and knots depends primarily upon human ability rather than upon actual characteristics of the various constituents of the material.

I have observed that aside from the good chips or fibre bearingmaterial, the clean logs 3 cmbody the following undesirable constituents, namely, decayed or rotten wood, bark and knots. I have also ascertained from various reliable sources that if the logs 3.are reduced to chips of approximately the same shape and size, and based upon the relative specific gravity and average moisture content of the constituents,

Good chips are lighter than rotten wood by 0.031 Good chips are lighter than bark by 0.175 Good chips are lighter than knots by 0.181

Thus the good chips are the lightest of all four of the log constituents, and my present improved process is based primarily upon this fact.

Referring specifically to Fig. 2 of the drawing,

my new process as disclosed diagrammatically therein, comprises the following steps. The roughly debarked logs 3 aretransferred from the stock pile M to a hot water pond [5 from whence the logs are subjected tofurther thorough cleansing in a rotary scrubber or washing drum the prior methods.

l6. From the scrubbing drum IS the clean logs 3 are passed through the chipper l1 and the resultant chips are subjected to a chip breaker Hi. The reduced chips from the breaker l8 are then delivered to a multiple deck screen IQ for the initial removal of the bulk of the excessively fine material which is sent directly to the boilers, and for further separation of the oversize material which is passed to another chip breaker and is returned to the screen. The properly graded chips delivered from the screen 19 are then subjected to classification in a classifier 2|. The classifier 2| may be of various types adapted to separate particles according to the specific gravity thereof, and since it is preferable to have the 2:

chips in relatively dry condition, the classification will be facilitated by utilizing air currents or jets ,to stratify the constituents of the uniformly reduced chips treated in the classifier 2|. While classifiers of this general type have long been successfully utilized in the mining and other industries, they have not heretofore been used process, and to the precise types of apparatus mentioned herein as being useful in carrying on the process, for various modifications within the scope of the appended claims may occur to persons skilled in the art.

I claim:

1. The process of treating logs and of converting the same into pulp, which comprises, roughly debarking the logs, subjecting the logs to a cleansing solution, externally scrubbing the logs to remove gritty substances and residual bark therefrom, reducing the logs to chips, breaking the chips into smaller chips, removing under and over size material from the chips to produce rel atively clean chips of approximately uniform size, advancing the sized chips in dry condition and in the form of a relatively loose layer of approximately uniform thickness along a reciprocable table provided with rifiles, and subjecting the layer to penetrating jets of air to pneumatically remove the objectionably light and heavy in the paper pulp industry, and the residual the chips, rotten wood, bark and knots, so that if the particles of all of these constituents are of approximately the same size and shape, they can be effectively separated in a classifier such as a reciprocable table havinga slow forward motion and a quick return motion, and provided with riiiles and orifices for delivering jets of air up- 7 wardly through the riffled surface. While considerable changes in the construction of present concentrating tables of this type appear desirable when classifying materials such as wood chips, these changes are of a mechanical nature, and the proper length of the table, the size of the ritlles, the air pressure required, and the speed of reciprocation, may vary somewhat in treating different kinds of pulp wood chips. It will be noted that my new process of Fig. 2 of the drawing, differs from the prior art process of Fig. 1 of the drawing. in that it entirely omits the manual removal of the rotten Wood, bark and knots, and depends solely upon the classifier for insuring such removal. The classification is carried on automatically and may obviously be effected at much lower cost than that of the manual labor. The improved step of classification will moreover insure more effective removal of undesirable particles, without wasting any of the good chip bearing material. By means of the improved classification method, particles of foreign matter such as dirt will also be more effectively removed from the good chips, thus absolutely insuring the production of better final product than has heretofore been possible with It might also be desirable to utilize several of the concentrating tables or classifiers 2| in series, in order to insure even more accurate classification, and the good chips may in this manner be separated into several grades for the purpose of manufacturing difierent grades of paper, and as previously indicated, the classifier 2i may be of various types preferably utilizing air currents to effect the separation of the grades.

It should be understood that it is not desired to limit this invention to the exact steps of the materials from the good chips.

2. The process of treating logs and of converting the same into pulp, which comprises, roughly debarking the logs, subjecting the logs to a cleansing solution, externally scrubbing the logs to remove gritty substances and residual bark therefrom, reducing the logs to chips, breaking the chips into smaller chips, removing under and over size material from the chips to produce relatively clean chips of approximately uniform size, advancing the sized chips in dry condition and in the form of a relatively loose layer of approximately uniform thickness along a reciprocal table provided with riflles, and subjecting the layer to penetrating jets of air to pneumatically remove the objectionably light and heavy materials from the good chips while simultaneously segregating the good chips into separate grades.

3. The process of treating logs and of converting the same into pulp, which comprises, roughly debarking the logs, subjecting the logs to a cleansing solution, externally scrubbing the logs to remove gritty substances and residual bark therefrom, reducing the logs to chips, removing under and over size material from the chips to produce relatively clean chips of approximately uniform size, advancing the sized chips in dry condition and in the form of a relatively loose layer of approximately uniform thickness along a reciprocable table provided with riflles, and subjecting the layer to penetrating jets of air to pneumatically remove the objectionably light and heavy materials from the good chips.

4. The process of treating logs and of converting the same into pulp, which comprises, roughly debarking the logs, subjecting the logs to a cleansing solution, externally scrubbing the logs to remove gritty substances and residual bark therefrom, reducing the logs to chips, removing under and over size material from the chips to produce relatively clean chips of approximately uniform size, advancing the sized chips in dry condition and in the form of a relatively loose layer of approximately uniform thickness along a reciprocable table provided with riflies, and subjecting the layer to penetrating jets of air to pneumatically remove the objectionably light and heavy materials from the good chips while simultaneously segregating the good chips into separate grades.

ARTHUR T. WARD. 

